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Jeff Epler c0550ad073
uf2 instructions
2022-01-12 12:54:28 -06:00
esp-idf@8bf14a9238 simplify 2022-01-07 15:50:16 -06:00
main Add pulse per minute/hour and "per second, exclusive" 2022-01-12 12:45:49 -06:00
uf2@1421ca7fe7 Add pulse per minute/hour and "per second, exclusive" 2022-01-12 12:45:49 -06:00
.gitignore Make it uf2'able 2022-01-12 12:46:24 -06:00
.gitmodules Add pulse per minute/hour and "per second, exclusive" 2022-01-12 12:45:49 -06:00
CMakeLists.txt Add neopixel for status 2022-01-07 16:34:13 -06:00
Makefile Make it uf2'able 2022-01-12 12:46:24 -06:00
partitions.csv Make it uf2'able 2022-01-12 12:46:24 -06:00
README.md uf2 instructions 2022-01-12 12:54:28 -06:00
sdkconfig.defaults Make it uf2'able 2022-01-12 12:46:24 -06:00

README.md

wifi-ntp-pps

Produce a pps signal reasonably well synchronized to NTP. The duty cycle is 100ms on (starting at the top of the second), 900ms off. Jitter is very high relative to GPS or even WWVB, but long term accuracy should be extremely good thanks to NTP.

(In practice, we measured the thing against a GPS-derived PPS signal for awhile, and saw the signal moving around +-20us compared to GPS, which is really pretty amazing.)

Installing and setting up esp-idf

One time set-up:

git submodule update --init
esp-idf/install.sh

(Note that this will fail if you've previously done . esp-idf/export.sh; use a fresh terminal if you have to (re)install esp-idf)

Set environment variables in current shell until exit:

. esp-idf/export.sh

Configuring wifi-ntp-pps

Open the project configuration menu (idf.py menuconfig):

  • Configure Wi-Fi under "Example Connection Configuration" menu. See "Establishing Wi-Fi or Ethernet Connection" section in examples/protocols/README.md for more details.

  • Select the board type (Adafruit QT Py or Adafruit Feather)

  • Select an ntp server. Ideally, a local server. Otherwise, pool.ntp.org can be used. The default will not work.

  • Optionally, turn down LWIP_SNTP_UPDATE_DELAY; the default is 1 hour. For a local NTP server something smaller like 30000 (30 seconds) is probably fine.

Compiling

make

Flashing

Plug in the device via USB and double-click the RESET button to enter the UF2 bootloader. Copy (or drag & drop) app.uf2 onto the boot drive.

Output pins

The "A0" pin gets a 1PPS output with the rising edge placed near the top of the second.

"A1" gets a pulse-per-minute, "A2" gets pulse-per-hour, and "A3" is "exclusive PPS": True once per second but only if it is not the hour or the minute, i.e., A3 = A0 & ~(A1 | A2).

Status indicator

The on-board neopixel gives the board status:

  • Black: power off or crashed
  • Solid red: never connected to wifi or crashed
  • Blinking red: never got NTP sync since power on
  • Blinking cyan: connected & got NTP sync in last 10s (sync is nominally every 30s, free-running timer)
  • Blinking green: connected & got NTP sync since power on